Interfacial thermal conductance between few to tens of layered-MoS2 and c-Si: Effect of MoS2 thickness

Abstract

We report a systematic investigation of interfacial thermal conductance (Gk) between few to tens-layered mechanical exfoliated molybdenum disulfide (MoS2) and crystalline silicon (c-Si). Based on Raman spectroscopy, we find Gk at room temperature increases with increased layer numbers of MoS2 from 0.974 MW m-2 K-1 to 68.6 MW m-2 K-1. The higher Gk of thicker samples reveals their better interface contact with the substrate, leading to accordingly improved interfacial energy coupling. Molecular dynamics (MD) simulations are conducted to interpret and compare with the experimental observations. MD simulations predict a thermal conductance in the range of 53~77 MW m-2 K-1 , which agrees well with the upper bound Gk measured in our work. The thickness dependence of measured Gk reflects the improved interface spacing for thicker MoS2 samples. This phenomenon is further confirmed by the Raman intensity enhancement study by the interface spacing and local optical interference calculations.

Thermal Transport in 2D Semiconductors—Considerations for Device Applications

“…By changing the thickness of the channel and increasing the spacing between the sample and substrate, the interface thermal transport could be tuned significantly. Layer‐dependent interface thermal conductance of MoS 2 with c‐Si substrate was measured by means of micro‐Raman spectroscopy, which increases monotonically with the number of layers . Typically, the interface spacing leads to a higher Raman intensity and disturbs the local interface thermal transport as well.…”

“…[136] The variations in the measured interface thermal conductance probably originate from the different interface quality prepared by the wet transfer method. [138] Higher values obtained are possibly due to the better interface quality in the absence of polymeric residues. [139] Temperature also affects the interface thermal transport as shown in Figure 7b, where the thermal boundary conductance (TBC) of MoS 2 -SiO 2 exhibits a T 0.65 dependence.…”

“…Although MD simulations show that the interface thermal conductance of MoS 2 on Au substrate is as high as 135–221 MW m −2 K −1 , the results obtained by the Raman technique are considerably lower–0.44 ± 0.07 MW m −2 K −1 for MoS 2 ‐Au, 1.94 MW m −2 K −1 for MoS 2 ‐SiO 2 , 17.0 MW m −2 K −1 for MoS 2 ‐h‐BN, and 15 MW m −2 K −1 for MoS 2 ‐AlN . The variations in the measured interface thermal conductance probably originate from the different interface quality prepared by the wet transfer method . Higher values obtained are possibly due to the better interface quality in the absence of polymeric residues .…”

“…d) Layer‐dependent interface thermal conductance of MoS 2 ‐c‐Si deduced from Raman sensitive E 2g 1 and A 1g modes. Reproduced with permission . Copyright 2017, Elsevier.…”

“…The interface spacing would impair the interatomic forces between MoS 2 and substrates. Therefore, due to the higher interfacial energy coupling, thicker MoS 2 usually shows a better interface contact and the interface thermal conductance increases from 0.974 to 68.6 MW m −2 K −1 with increasing number of MoS 2 layers . The thickness‐dependence of interface thermal conductance is shown in Figure d.…”